Video sensors based on modern computer architectures are able to detect objects moving in a directional manner in image sequences of stationary cameras. The monitoring normally tracks the beginning point at which predefined threshold values with respect to segment distance or size are exceeded. Such condition is detected by changes in the image signal caused by the movement of objects such as persons, for example, whereupon a corresponding signaling or image recording takes place. In this manner, the objective of raising an alarm concerning an unauthorized entry may be realized.